Automatic lathe

ABSTRACT

An automatic lathe wherein a plurality of cutters are provided in confronting relation to a rotating rod material, and the movement of the said rod material and the said cutters are controlled according to a working information stored in a tape or card, whereby a complete parts is obtained automatically according to the said working information.

United States Patent Takano et al.

[151 3,680,415 [451 Aug. 1,1972

AUTOMATIC LATHE Inventors: Hirotugu Takano; Toshitsugu Inoue,

both of Kyoto, Japan Assignee: Matsushita Electric Industrial Co.,

Ltd., Osaka, Japan Filed: May 19, 1970 Appl. No.: 38,695

Foreign Application Priority Data May 26, 1969 Japan ..44/42356 US. Cl..82/19, 29/37 A Int. Cl. ..B23b 3/28 Field of Search ..29/37 A; 82/19[56] References Cited UNITED STATES PATENTS 1,798,143 3/1931 Dardelet..82/l9 FOREIGN PATENTS OR APPLICATIONS 771,689 4/1957 Great Britain..82/l 9 Primary Examiner-Francis S. I-lusar Att0rneyStevens, Davis,Miller & Mosher 5 7] ABSTRACT An automatic lathe wherein a plurality ofcutters are provided in confronting relation to a rotating rod material,and the movement of the said rod material and the said cutters arecontrolled according to a working information stored in a tape or card,whereby a complete parts is obtained automatically according to the saidworking information.

8 Claims, 25 Drawing Figures PATENTEDAUG 1 m2 3.680.415

sum 010F10 FIG. I PRIOR ART FIG. 2 FIG. 3

PRIOR ART PRIOR ART #ZZA/ME INVENTORS 7 BYJ ATTORNEYS PAIENTEDAUH 23.680.415

sum 02 or 10 FIG. PRIOR ART PATENTEDMIBHI 912 3.680.415

SHEET an 0F 10 PATENTED IIIII; I I972 3.680.415

SHEET us [1F 10 I44 FIG. I 4 ROTATIONAL DIRECTION OPERAWN 3mm DESIG CODEINSTRUCTING CODE I I45 A4? MAN. TAPE 4 o com 80 READER Eu) I 522""COLLET CHUCK Lg DECODER 7 85 DRILL MOUNT I 1 I I J2 PFARTS E EEEIII=I REED 8 *2 g ii g gg =DEuvERYcHuTE U U I Q I i I'- s aw I I ifii L. J INO. I CLUTCH NO. 2 I50] d NO. 3 NUM 02 NO. 4 RE? 20 NO. 5 E5 NO. 6suBTRAc- 35 N0. 7 TION CKT P- |5| T|M|N Z I-- MAIN SHAFT QULSE CONTSQL8% DRIVING MOTOR GEN MEANS fi J o 2 cuTTINe TOOL 7 RIvINs MOTOR Q COIECTION I55 E No. I- No. 7 D CLUTCH sw AUTO DIM c CUTTING TOOL MEASURING482' @9552 m MEANs MEANS -z MAIN SHAFT MEANS g LIMIT sw 1 12. CUTTINGTOOL PARTS PARTS Q ORIGIN DETECTDN sw MA|N SHAFT ORIGIN COUNTERDETECTION sw PATENTEDMHW 3.680.415

sum 08UF10 PATENTEDms usn 3.680.415

SHEET nsur 10 FIG. 20

FIG. 2|

AUTOMATIC LATHE This invention relates to an automatic lathe.

The most typical one of the conventional automatic lathes is aSwiss-type automatic lathe, which will be described hereunder withreference to FIGS. 1 to 6. In turning a rod material, first of all, therod material 1 is rotated and a cutter 2 is fed in the radial directionof the rod material 1 or in the direction of the arrow a, to turn theperipheral wall of the rod material as shown in FIG. 1. The depth ofturning is variable depending upon the degree of feeding of the cutter2. Then, a cutter 3 is fed in the axial direction of the rod material 1or in the direction of the arrow b and pressed against the end face ofthe rod material, whereby the end face of the rod material 1 is cut. Inthis case, a hole may be formed in the end face of the rod material 1 byusing a drill as the cutter 3. In the turning operation, the rodmaterial is moved in the direction of the arrow 0. An automatic lathe isconstructed according to such basic arrangement of the rod material 1and the cutters 2, 3.

In the actual Swiss-type automatic lathe, as shown in FIG. 2, a firstcutting tool 4, a second cutting tool 5, a third cutting tool 6, afourth cutting tool 7 and a fifth cutting tool 8 are arranged radiallyof a rod material 9 to be cut. The first cutting tool 4 and the secondcutting tool are mounted on a rockable cutter mount 11 which is rockableabout a fulcrum 10. Thus, it will be seen that, in the rocking motion ofthe rockable cutter mount 11, the second cutting tool 5 moves away fromthe rod material 9 as the first cutting tool 4 approaches the rodmaterial, whereas the first cutting tool 4'moves away from the rodmaterial as the second cutting tool 5 approaches the rod material. Whenthe rockable cutter mount 11 is in a horizontal position, both the firstcutting tool 4 and the second cutting tool 5 are held out of contactwith the rod material 9. The rocking motion of the rockable cutter mount11 is caused by a cam 13 which is mounted on a cam shaft 12 to berotated thereby and held in engagement with a cam follower l4, fixed tothe cutter mount 11, to cause it to move up and down, the cam shaft 12being driven at a constant speed. The cam follower 14 is held inpressure contact with the cam 13 under the biasing force of a spring 15.Thus, the rockable cutter mount 11 rocks precisely in accordance withthe profile of the cam 13. On the other hand, the third cutting tool 6,the fourth cutting tool 7 and the fifth cutting tool 8, which are calledvertical cutting tools, have the same construction, so that adescription will be given only on the third cutting tool 6 hereunder. Acontrol cam 16 for the third cutting tool 6 is fixedly mounted on thecam shaft 12 and a cam follower 19 provided on an arm 18 is yieldablypressed against the control cam 16 by a spring or the like (not shown).The arm 18 is pivotable about a pivot pin 17 and has one end pivotallyconnected to one end of a link 20. The link 20 has the other endpivotally connected to one end of an arm 22 which is pivotable about apivot pin 21. The other end of the arm 22 is provided with a set screw23 which is in abutting engagement at one end with the end face of acutter mount 24 which holds the third cutting tool 6. It will,therefore, be understood that when the control cam 16 is rotated, thecam follower 19 makes a vertical move ment, following the profile of thecontrol cam and the vertical movement is transmitted to the link 20 andthe arm 22 to move the third cutting tool 6 toward or away from the rodmaterial. Such movement of the third cutting tool 6 is controlled by theprofile of the control cam 16. Similarly, the movements of the fourthcutting tool 7 and the fifth cutting tool 8 toward or away from the rodmaterial are controlled by control cams 25, 25

respectively, which are also mounted on the cam shaft 12. Now, theconstruction of a drilling tool will be described hereunder. As shown inFIG. 4, a tool mounting shaft 26 is provided in alignment with the axisof the rod material 9. This tool mounting shaft 26 is constantly biasedbackward by a spring or the like (not shown) and has a drilling tool 27mounted therein. An arm 28 is pivotably mounted on a pivot pin 29, withone end located opposite to the rear end of the tool mounting shaft 26.The other end of the arm 28 is provided with a pin 31 which is insliding engagement with the cam surface of a barrel cam 30. A tool mount32 in which the tool shaft 26 is mounted, has another tool shaft 33mounted therein, and this tool mount 32 is pivotable about a pivot pin34 as shown in FIG. 5. An arm 35 is connected to the tool mount 32 atone end and the other end of the arm 35 is provided with a cam follower36, which is held in pressure engagement with a cam 37 under the biasingforce of a spring 38, the cam 37 being fixedly mounted on the cam shaft12. Thus, it will be seen that when the cam shaft 12 is driven, the toolmount 32 is pivoted about the pivot pin 34 by the cam 37 to bring eitherthe tool shaft 26 or 33 into axial alignment with the rod material 9.Further, the arm 28 is pivoted about the pivot pin 29 by the barrel cam30 and pushes the tool shaft 26 or 33 from the backside by one endthereof, so that the drilling tool mounted in the tool shaft is pressedagainst the end face of the rod material 9 to drill a hole therein.

The rod material is controlled as follows: In order to keepthe rodmaterial rotating and to effect forward or backward movement of the rodmaterial in relation with the respective tools, use is made of amechanism called material feeder. This material feeder is generallyindicated at 39 in FIG. 6. The rod material 9 is extended through thematerial feeder 39 and gripped therein by a collet chuck 40. The colletchuck 40 is operatively connected with a motor 44 through a pulley 41, abelt 42 and a pulley 43, to be driven thereby. On the collet chuck 40 ismounted a ring 45 which tighten the collet chuck 40 around the rodmaterial 9 when moved in the direction of the arrow d and releases thesame from the rod material when moved in the opposite direction. Thehorizontal movement of the ring 45 is effected by a cam 46 which ismounted on the cam shaft 12 and operates a cam follower 47 which isoperatively connected to the collet chuck through arms 48, 49.Therefore, whether the collet chuck 40 grips the rod material orreleases it is determined by the configuration of the cam 46. The rodmaterial 9 can be moved in the direction of the arrow e in FIG. 6, bypushing the material feeder 39 in the same direction by an arm 50against the biasing force of a spring 51, with the rod material beinggripped by the collet chuck 40. The arm 50 is connected at one end tothe material feeder 39 and caused to make a pivotal movement by a cam 52which is mounted on the cam shaft 12 and held in engagement with a camfollower 53 provided at the other end of said arm 50.

As will be apparent from the foregoing description, the conventionalSwiss-type automatic lathe is so constructed that the axial movements ofa plurality of cutting tools toward and away from the rod material andthe feeding of the rod material are all effected by a number of camsmounted on a single cam shaft 12. Therefore, it had the disadvantagethat the configurations of the respective cams become complicated as thefinal configuration of the desired part becomes compli'cated, whichrendered the design and manufacture of the cams difficult and even madeit impossible to produce the cams in such complicate configurations dueto the limited diameters of the cams. Another disadvantage is that allof the cams must be replaced with new ones every time when the type ofthe parts to be obtained is changed. Therefore, while the lathe may beused expense-wise forthe production of a parts in a quantity as large,forexample, as 10,000 or more, it cannot be used for the production ofthe parts in a lesser quantity because the preparatory expense and timeare too large to make the business profitable.

The present invention aims to obviate the foregoing disadvantages of theprior art automatic lathes. Namely, the first object of the invention isto provide an automatic lathe which is so designed that a workinginformation fed thereto externally is converted into an electric signaland a drive source is controlled by the electric signal, whereby themovements of a rod material to be worked and cutting tools for workingthe rod material are suitably controlled and a parts of desiredconfiguration is obtained.

Another object of the invention is to provide an automatic lathe of thecharacter described above, wherein cam plates each having a cam surfacein the shape of an Archimedes curve in cross-section are mounted on ashaft driven from the drive source, while cam followers are provided onthe driven elements such as the cutting tools and held in engagementwith the cam surfaces of the cam plates respectively, so that the drivenelements may be moved in proportion to the angle of rotation of theshaft, and the angle of rotation of the drive source is controlled,whereby the driven elements are moved precisely by the desireddimensions respectively.

Still other object of the invention is to provide an automatic lathe ofthe character described above, wherein the cam surface of each of thecam plates consists of a relatively small diameter portion defining anArchimedes curve of larger curvature and a relatively large diameterportion defining an Archimedes curve of smaller curvature, whereby thecutting tools are quickly moved toward the rod material when the rodmaterial is to be worked and are held remote from the rod material whenthe rod material is not to be worked.

Yet still other object of the invention is to provide an automatic latheof the character described above,

wherein each of the cam followers in engagement with the cam surface ofthe associated cam plate is slidably mounted on an arm connected to theassociated driven element, and the cam follower and said arm areoperatively secured to each other by means of a clutch mechanism whichis actuated by the electric signal, whereby the driven element isoperated or stopped accurately according to the working information.

Yet other object of the invention is to provide an automatic lathe ofthe character described above,

wherein means for detecting the state, of engagement or disengagement ofthe clutch mechanism is provided so as to prevent a plurality of cuttingtools from being fed concurrently toward the rod material and collidingagainst each other.

Yet other object of the invention is to provide an automatic lathe ofthe character described above, wherein a cutting tool mount rockablymounted on a pivot pin and having a pair of cutting tools fixed theretois provided with two cam followers, while cam plates each having a camsurface in the shape of an Archimedes curve in cross-section are mountedon a common rotary shaft for engagement with the respective camfollowers in such a manner thatthe cam surfaces thereof are opposite toeach other in the direction of inclination, one of the cam followersbeing fixed to the rockable cutting tool mount and the other one of thecam followers being mounted to the rockable cutting tool mount through aclutch mechanism, whereby cam plates of the same size as the cam platesfor the other cutting tools can be used for operating the pair ofcutting tools and the rockable cutting tool mount can be operatedwithout using a cam plate of particularly large size.

Further object of the invention is to provide an automatic lathe of thecharacter described above, wherein two drive sources are provided, ofwhich one is used to cause an axial movement of a material feeder havinga rod material to be worked securely gripped therein and another one isused to move a plurality of cutting tools provided in confrontingrelation to the rod material, both of the drive source and clutchmechanisms provided for the respective cutting tools being operatedaccording to a working information, whereby a parts in conformance tothe working information is obtained.

Yet further object of the invention is to provide an automatic lathe ofthe character described above, wherein an origin switch is provided inan incrementalopen loop type electrical control means adapted to controlthe drive source upon reading the working information, so as to detectthe position of the origin each time when one parts has been completed,and the angle of rotation of the drive source is controlled based on theposition of the origin, whereby even if a step error occurs in theelectrical control means through some unexpected reasons during working,it will not be accumulated in the following parts.

Still other object of the invention is to provide an automatic lathe ofthe character described above, wherein whether or not the parts has beenworked precisely in accordance with the working information is checkedby comparing the numerical value of the working information and thenumerical value of the signal obtained on rotation of a driven elementoperating shaft with each other, using the origin switch.

Still other object of the invention is to provide an automatic lathe ofthe character described above, wherein, in order to preclude the actualdimensions of the worked parts from becoming larger or smaller than thenumerical values of the working information, which is possible due towear of the cutting edge of the cutting tool or attachment of a foreignmaterial to the cutting edge of the same even if the cutting tool is fedprecisely, means is provided to actually measure the dimensions of theworked parts and adjust the numerical values of the working informationby an amount corresponding to the error, so that a parts of accuratedimensions may always be obtained.

Yet other object of the invention is to provide an automatic lathe ofthe character described above, wherein discrimination chutes areselectively positioned below a parts dropping position by the functionof solenoids which are actuated by the working information and a signalrepresentative of good or bad of a worked parts checked according to acheck instruction, whereby the worked parts are automaticallydiscriminated by the type and quality.

Still other object of the invention is to provide an automatic lathe ofthe character described above, wherein a drill mount movable toward theend face of the .rod material is rotatably supported by an arm operatedfrom the drive source and a plurality of drilling tools are mounted insaid mount, the tool mount being rotated by a solenoid operatedaccording to the working information, whereby the drilling tools areselectively positioned in a working position to work the 'end face ofsaid rod material.

Still other object of the invention is to provide an automatic lathe ofthe character described above, wherein a collet chuck is provided in thematerial feeder and opened or closed by a solenoid which is operatedaccording to the working information, whereby the rod material ispositively gripped by released from the collet chuck.

The present invention will be described in detail hereinafter withreference to the accompanying drawings, in which:

FIG. 1 is a diagram showing the basic relative position of a rodmaterial and cutting tools in normal tuming operation;

FIG. 2 is a view showing the essential portion of a conventionalSwiss-type automatic lathe as viewed in the axial direction of a rodmaterial;

FIG. 3 is a side view of the portion shown in FIG. 2;

FIG. 4 is a top plan view of a drill mount in the conventionalSwiss-type automatic lathe;

FIG. 5 is a back view of the drill mount;

FIG. 6 is a side view, partially broken away, of a material feederportion of the conventional Swiss-type automatic lathe;

FIG. 7 is a view showing briefly the entire construction of anembodiment of the automatic lathe according to the present invention;

FIG. 8 is a front view, partially broken away, of the positioncorrecting mechanism in the automatic lathe of FIG. 7;

FIG. 9 is a perspective view of the position correcting mechanism of theautomatic lathe for moving and controlling the drilling tool shaft, witha portion thereof broken away to show the essential portion;

FIG. 10 is a vertical cross-sectional view of a limit detector;

.FIG. 11 is a view showing the arrangement of the lead switches used inthe limit detector FIG. 12 is a vertical corss-sectional view of anorigin detector;

FIG. 13 is a view showing the arrangement of the lead switches of theorigin detector;

FIG. 14 is a block diagram showing the control system of the automaticlathe;

FIG. 15 is a diagram for explaining the operation of the positioncorrecting mechanism;

FIG. 16 is a circuit diagram for explaining the operation of a steppingmotor;

FIG. 17 is a timing diagram showing the current phase of the steppingmotor and the operation of the origin switch;

FIG. 18 is a diagram showing the operation of a cutting tool undernumerical control;

FIG. 19 is a view briefly showing the construction of a partsdiscriminating device;

FIG. 20 is a side view, partially broken away, of a chuck by which asample parts is taken out for measurement;

FIG. 21 is a side view of a parts measuring device;

FIG. 22 is a diagram for explaining the operation of the parts measuringdevice;

FIG. 23 is a diagram showing the output change of a differentialtransformer in the measurement of the dimensions of a parts;

FIG. 24 is a block diagram of an automatic dimension measuring unit; and

FIG. 25 is a diagram illustrating the principle of a linear cam.

An embodiment of the present invention will be described with referenceto FIGs. 7 to 25.

The automatic lathe of the present invention is generally composed of amachine tool unit to transmit the drive of a drive source to cuttingtools and a rod material, and a control unit to control the operation ofthe machine tool unit.

Of these two units, the machine tool unit will be explained at firsthereunder: The machine tool unit is further broadly divided into amaterial feeder unit and a cutting tool mounting unit.

Referring to FIG. 7, numeral designates a material feeder. Although acollet chuck to grip or release an elongate rod material 61 and a motorto impart rotation to the rod material are not shown, they areessentially same as those used in the conventional Swiss-type automaticlathe and a description thereof will be omitted. The material feederunit of the invention differs from that of the conventional Swiss-typeautomatic lathe, in the manner of operating a ring (not shown) providedaround the collet chuck and the manner of operating the material feeder60. Namely, in the present invention, use is made of an electromagneticcoil 62 to operate the ring, and an arrangement is made such that whenthe electromagnetic coil 62 is energized, an arm 63 is pulled andthereby the ring is moved to cause the collet chuck to grip the rodmaterial 61, whereas when the electromagnetic coil 62 is de-energized,the arm 63 is returned to the original position as by a spring, wherebythe collet chuck releases the rod material 61. The material feeder 60 isconstantly biased backward by a spring 64 so as to eliminate aback-lash, and is moved forward against the biasing force of the spring64 by an arm 66 pivoted on a pin 65. A steppingmotor 67 is used as adrive source for the material feeder. Namely, the drive of the steppingmotor 67 is transmitted from the drive shaft 68 of the motor to a camshaft 71 through intermeshing gears 69, 70, to rotate a linear cam 72mounted on the cam shaft. The rotating linear cam 72 causes a movementof a cam follower 73 in engagement with the cam surface of the linearcam and the movement of the cam follower 73 is trans: mitted to the arm66 through an arm 74. Thus, the material feeder 60 is moved by the arm66.

The linear cam 72 is an essential element in the present invention andwill be described in further detail hereunder. The linear cam 72 is sodesigned that the lift (inclination) of the cam surface is in a fixedproportional relation with the angle of rotation. Namely, the camsurface of the cam 72 has an Archimedes curve. In this specification, acam such as the cam 72 whose cam surface defines an Archimedes curve isreferred to as linear cam.

Numeral 75 designates an origin detector provided on the drive shaft 68of the motor 67, which serves to determine the position of the materialfeeder 60 when the material feeder is to be returned to its originalposition upon completion of working of one parts, and the constructionand function of the origin detector will be described later. Numeral 76designates a limit switch provided on the cam shaft 71, to detect theangle of rotation of the cam shaft 71, and the construction and functionof the limit switch will be described later.

Now, the cutting tool mounting unit will be described. As shown inFIG.7, a first cutting tool 77, a second cutting tool v78, a third cuttingtool 79, a fourth cutting tool 80 and a fifth cutting tool 81 arearranged radially of the rod material 61. The first cutting tool 77 andthe second cutting tool 78 are mounted on a rockable tool mount 82,while the third cutting tool 79, the fourth cutting tool 80 and thefifth cutting tool 81 are mounted on cutting tool mounts 83, 84 and 85.,respectively. The tool mounts 83, 84 and 85 are operated by links 86(only one being shown) and arms (not shown) as in the conventionalSwiss-type automatic lathe. In the present invention, however, the wayin which the rockable tool mount 82 and the tool mounts 83, 84 and 85are operated is different from that in the conventional Swiss-typeautomatic lathe. Namely, in the present invention the drive shaft 88 ofa stepping motor 87 and a cam shaft 89 are operatively connected witheach'other by intermeshing gears 90, 91, and linear cams 92, 93 foroperating the rockable tool mount 82 are mounted on the cam shaft 89 insuch a manner that the lifts thereof are in opposite directions to eachother. The cam surfaces of the linear earns 92, 93 are in engagementwith cam followers 94, 95 respectively which provided on an arm 96connected to the rockable tool mount 82. In this case, the cam follower94 is fixed to the arm 96, whereas the cam follower 95 is connected tothe arm 96 through a clutch mechanism to be described later, in such amanner that it isslidable relative the arm 96 when the clutch mechanismis disenergized to and can be fixed to the arm 96 by energizing. Therockable tool mount 82 is constantly biased by a spring 97 to rotateclockwise unless the rotation is restricted by a stopper 118. Therefore,either the cam followers 94 or 95 is held in engagement with the linearcam 92 or 93. Describing the operation of the rockable tool mount 82 infurther detail, when the cam follower 95 is secured to the arm 96 byenergizing the clutch mechanism, during rotation of the cam shaft 89 innormal direction or in the direction of the arrow f, the rockable toolmount 82 is rotated by the cam surface of the linear cam 92, so that thesecond cutting tool 78 is brought into contact with the rod material 61to turn the same. In contrast, when the clutch mechanism is de-energizedduring rotation of the cam shaft 89 in the direction of the arrow f, camfollower is slidable relative to the arm 96 and the rockable tool mount82 is rotated in an opposite direction by the cam follower 94 and thelinear cam 93, so that the first cutting tool 77 is brought into contactwith the rod material 61 to turn the same.

When a solenoid for the stopper 118 is in the deenergized state therebyprojecting a pin 300 of the stopper as shown in FIG. 7, the rockabletool mount 82 abuts against the pin 300 of the stopper 118 under thebiasing force of the spring 97 and is held horizontally. However, whenthe solenoid is energized and the pin of the stopper 118 is retracted,the rockable tool mount 82 isreleased from the stopper and rotated underthe biasing force of the spring 97, so that either the cam follower 94or 95 are brought into engagement with the linear cam 93 or 92. Thelinear cam 93 is for controlling the movement of the first cutting tool77 and the linear cam 92 is for controlling the movement of the secondcutting tool 78. The use of two linear cams for controlling thecorresponding cutting tools as described above is one of thecharacteristic features of the present invention. Because if only onecam is used for causing a rocking motion of the rockable tool mount, anarrangement must be made such that the rockable tool mount is held in ahorizontal position when the cam follower is located at an intermediatepoint of the portion of the cam surface from the valley to the crest ofthe cam surface, and the half of the portion from the intermediate pointto the crest is used for controlling the second cutting tool, whereasthe other half of the same is used for controlling the first cuttingtool. Thus, only a half of the revolution of the cam shaft can be usedfor the control of the respective cutting tools and accordingly thecontrollable range becomes small. As contrasted, when two linear camsare used as in the present invention, one full revolution of the camshaft can be used for the control of the respective cutting tools.

On the cam shaft 89 are also mounted linear cams 98, 99 and 100 forcontrolling the tool mounts 83, 84 and 85, respectively, and camfollowers 104, and 106 .each provided on an arm through a clutchmechanism are in engagement with the cam surfaces of the linear cams 98,99 and 100, respectively. The relationship between the linear cams 98,99, 100 and the cam followers 104, 105, 106 constitutes an essentialfeature of the invention and, therefore, will be described in detailwith reference to FIG. 8. Referring to FIG. 8, there is shown therelationship between the linear cam 98 and the cam follower 104. Thearrangement of other linear earns 99, 100 and cam followers 105, 106 isthe same as that of FIG. 8 and will not be described herein.

The linear cam 98 is so designed that the angle of rotation and the lift(radius) of the cam surface are in proportional relation to each other,and the lift thereof is formed in two steps. Namely, the linear cam 98has a cam surface which consists of two different Archimedes curves. Aswill be seen in FIG. 25 which shows the principle of the linear cam, theinclination of the portion of the cam surface from a point A to a pointB is made constant relative to the angle of rotation and is also madesteep and the inclination of the portion from the point B to a point Cis also made constantrelative to the angle of rotation but is madegradual relative the inclination of the portion from the point A to thepoint B. In practice, the cam surface of the linear cam 98 is so shapedthat the portion from the point A to the point B has a lift of 0.1 mmfor each angle of rotation of 1 and the portion from the point B to thepoint C has a lift of 0.02 mm for each angle of rotation of 03. Therotating speed of the stepping motor 87 is reduced by the gears 90, 91such that the cam shaft 89 having the linear cam 98 mounted thereon willrotate 0.3 for every one step rotation of the stepping motor. Thestepping motor 87 rotates one step each time one electric pulse is giventhereto. FIG. 8 shows that the clutch mechanism is in the engagedposition. Namely, a clutch coil 107 is energized and an armature 108 isattracted to the right hand in FIG. 8 thereby pushing a clutch pin 1 10against the biasing force of a spring 109, so that, the other end of theclutch pin 110 is received within a notch 111 formed in the camfollower'104. When the linear cam 98 is rotated in the direction of thearrow f under such condition, the cam follower 104 is lifted and causesthe arm 101 to rotate about a pivot pin 112, through the engagementwiththe clutch pin 110. The rotation of the arm 110 is transmitted tothe link 86 through a pivot pin 113 and thence to the tool mount 83through a separate arm, to move the third cutting tool 79 toward the rodmaterial 61. In this case, the ratio of the distance from the pivot pin112 of the arm 101 to the pivot pin 113, to the distance from the pivotpin 112 to the tip of the cam follower 104 is made 1 2 for enhancing theprecision. Therefore, the tool mound 83 moves 0.01 mm on every one steprotation of the stepping motor 87.

Further, when the cam follower 104 is in engagement with the portion ofthe cam surface of the linear cam 98 from the point A to the point B,the lift of the cam follower 104 is large relative to the angle ofrotation of the linear cam 98 and, therefore, the third cutting tool 79is quickly moved toward the rod material 61. Namely, when the camfollower 104 is at a point adjacent the point A, the third cutting tool79 is held remote from the rod material 61. This is for the purpose ofpreventing the chip, produced by turning of the rod material 61 by theother cutting too, from wrapping around the third cutting tool 79. Thelift of the portion from the point A to the point B is made large sothat the third cutting tool 79 may quickly be fed over such a remotedistance and the operation efficiency may be enhanced. When the camfollower 98 has reached the point B, the third cutting tool 79 ispositioned very close to the rod material 61, and thereafter the camfollower 104 is displaced at a low speed according to the small lift ofthe linear cam 98 provided by the portion beyond the point B. Therefore,the third cutting tool 79 is fed slowly toward the axis of the rodmaterial 61 to turn the rod material. Furthermore, the arrangement ismade such that the clutch pin 109 is disengaged from the notch 111 ofthe cam follower 104 only when the cam follower is located at the pointA and is inserted into the notch only when the cam follower is locatedadjacent the point A. This means that the next other cutting tool is notallowed to be fed unless the working cutting tool is sufficientlyretracted and therefore collision of the cutting tools against eachother is prevented. The linear cams 92, 93 also have a cam surfaceconsisting of two types of inclination, similar to the linear cam 98described above.

In FIG. 8, numeral 114 designates a magnet which is mounted on a plate115 connected to the armature 108, in substantially opposed relation toa lead switch 116. This magnet 114 is a permanent magnet and operated atthe same time when the armature 108 is attracted upon energization ofthe clutch coil 107, to actuate the lead switch 116. The lead switch 116is opened when the armature 108 returns to its original position underthe biasing spring 109. This lead switch 116 constitutes a detectingcircuit to verify the operation of the clutch pin 110 and to prevent aphenomenone wherein two or more cutting tools are fed concurrently as aresult of the clutches provided on the other cam followers beingenergized concurrently. Numeral 117 designates a Bakelite plate formounting the lead switch 1 16 thereon.

Referring back to FIG. 7, cutting tools 119, 120 for working the endface of the rod material 61 are operated in the following manner:Namely, these cutting tools 119, 120 are mounted in tool shafts 121, 122respectively which are operated by a barrel cam 123 mounted on the camshaft 89. The barrel cam 123 has a two-step linear cam surface and a camfollower 124 moves relative to the barrel cam along the cam surface,whereby an arm 125 is caused to make a pivotal movement about a pivotpin 125 and the tool shaft 121 or 122 is pushed by the other end of thearm 125. Thus, the cutting tool 119 or 120, mounted in the tool shaft121 or 122, is pushed against the end face of the rod material toperform a work such as drilling. The cam follower 124 is controlled by aclutch 126.

The clutch 126 is, as shown in FIG. 9, essentially the same inconstruction and function as that of FIG. 8 and detailed descriptionthereof will be omitted. The only difference is that in the clutch ofFIG. 9 the clutch pin 1 10 of the clutch shown in FIG. 8 is used as thecam follower 124 as it is. Namely, when a. coil 107 is energized, anarmature 108 is attracted, so that the cam follower 124 is projected forengagement of the cam surface of the barrel cam 123 and the movement ofthe cam follower 124 is transmitted to the arm 125. On the other hand,when the current supply to the coil 107 is interrupted, the cam follower124 is disengaged from the cam surface of the barrel cam 123 and hencethe arm 125 is held stationary.

The tool shafts 121, 122 to be operated by the arm 125 are slidablysupported in a drilling tool mount 127 which in turn is pivotablymounted on a pin 128. A spring 129 is anchored to one side of thedrilling tool mount 127 with respect to the pin 128, to pull the toolmount, while a cutting tool selection solenoid 130 is provided on theother side of the tool mount 127. Therefore, when the solenoid 130 isnot energized, the tool mount 127 is pulled by the spring 129 to locatethe drilling tool 119 opposite to the end face of the rod material 61,whereas when the solenoid 130 is energized, the tool mount 127 is causedto rotate about the pin 128 by the solenoid 130 against the biasingforce of the spring 129, to locate the drilling tool 120 opposite to theend face of the rod material 61. After the drilling tool 119 or 120 hasbeen positioned opposite to the rod material 61 in the manner described,the tool shaft 121 or 122 is work can be performed on the end face ofthe rotating rod material.

The drive shaft 88 and the cam shaft 89 are provided thereon with anorigin detector 131 and a limit switch 132 respectively which areidentical in construction with the aforesaid origin detector 75 andlimit switch 76. 7

Now, description will be given on the limit switch 132 with reference toFIGS. and l 1. A linear cam always provides a large fall when rotatedcontinuously in one direction and a steep upward gradient which cannotbe followed, when rotated continuously in an opposite direction. Namely,that is the portion between the point A and the point C in FIG. 8. Sincethis portion of the cam surface cannot be used, it becomes necessarytoprovide limit switches immediately before the point A and the point C,to emit a signal to stop the stepping motor. For convenience ofexplanation, the former is called retraction limit and the latter iscalled advance limit. The limit switch 132 includes a boxshaped housingcomposed of a cover 133 and an insulating plate 134 and the box-shapedhousing is fixed unmovably with aspace to the cam shaft 89. On theinsulating plate 134 are provided a lead switch 135 for advance limitand a lead switch 136 for retraction limit. An arm 137 is fixed to thecam shaft 89 and a magnet 13.8 is fitted to the arm at a locationopposite to the lead switches 135 and 136. The limit switch 132 of theconstruction described above operates in such a manner that, when thecam shaft 89 is rotated in normal direction and the magnet 138 carriedthereon approaches the lead switch 135, the contacts of the lead switch135 are closed to stop the rotation of the stepping motor 87, and whenthe magnet 138 approaches the lead switch 136, the contacts of the leadswitch are closed to stop the rotation of the stepping motor 87.

Next, description will be given on the origin detector 131 withreference to FIGS. 12 and 13. The origin detector 131 includes abox-shaped housing composed of a cover 139 and an insulating plate 140,and the boxshaped housing is fixed unmovably with a space to the driveshaft 88 of the stepping motor 87.

The insulating plate 140 is provided thereon with a lead switch 141,while an arm 142 fixed on the drive shaft 88 is provided thereon with amagnet 143 so as to be opposed by the lead switch 141. Therefore, whenthe drive shaft 88 is rotated and the magnet 143 approaches the leadswitch 141, the contacts of the lead switch are closed and a signal isemitted which is an origin signal. This origin signal is emitted at aposition opposite to the point B of the linear cam 98, and the angle ofrotation of the drive shaft 88 is determined based on this position. Thelift of the linear cam 72 is one step and, therefore, the origin signalis emitted at a point adjacent the stepped portion.

Hereinabove, the construction of the machine tool unit has beendescribed. The control unit will now be described hereunder:

The construction of the control unit is as shown in the block circuitdiagram of FIG. 14. The lines going out from and coming into the blockcircuit diagram are all connected to the electric elements of themachine tool unit respectively for transmission of electric signalstherethrough to perform a turning operation automatically. Theoperations of the respective blocks will be explained in sequencehereinafter. First of all, a paper tape 144 is provided therein withperforations representing the controlling information which is indicatedin terms of predetermined numerals, alphabets or symbols. When a tapereader 145 reads the tape 144, all the information thus read is fed to adecoder 146, wherein the information is sorted by the type of the codesignified by the information. In case when the information is a partssorting code, a solenoid control means 147 is actuated to energize aparts discrimination solenoid to be described later. In case when theinformation is a cutting tool designating code, a cutting tool selectionclutch control means 148 is actuated to operate a pertinent cutting toolselection clutch. The code is further fed to a motor control means 149,which in turn issues an instruction to operate either the main driveshaft driving motor or the cutting tool operating motor. In case whenthe information is a rotational direction designating code, the codesignal is fed to the motor control means 149, which in turn switches themotor operating circuit from normal rotation to reverse rotation or viceverse. A numeral code is set in a numeral register 150 to be memorizedtherein, the numeral register is of the type of four digit of decimalnumbers. A speed designating code acts on a pulse generator 151 todetermine the frequency of the pulse generated thereby. This pulse is astep pulse to operate the stepping motor and the frequency thereofdetermines the rotational speed of the motor. A correction instructingcode is fed to a timing control means 152 to effect a positionalcorrection to be described later. An operation start instructing code isfed to the timing control means 152 and a numerical control operation iscommenced only after the timing control means receives the said code.

Namely, when the operation start instructing code enters the timingcontrol means, a signal is given to the tape reader to stop itsoperation and successively thereafter a pulse generating instruction isgiven to the pulse generator 151, whereby the pulse generator starts togenerate pulses continuously. The first one pulse is fed to the motorcontrol means 149 to rotate either the stepping motor for the main driveshaft or the stepping motor for the cutting tool one step in thedirection previously designated. The first pulse is also fed to thetiming control means 152 and thence to a subtraction circuit 153 tosubtract l from the numeral memorized in the numeral register 150. Forinstance, when the numeral memorized in the numeral register 150 is 100,it become 99 and this numeral 99 is memorized in the numeral register.The numeral memorized in the numeral register is transmitted to a zerodecision circuit 154 on each subtraction of the numeral but no signalwill be emitted from the zero decision circuit 154 unless the numeralbecomes zero. When the next pulse is generated from the pulse generator151, the stepping motor is rotated one step and at the same time numeral1 is subtracted from the numeral memorized in the numeral register 150by the function of the subtraction circuit 153, as described above. Whenthe numeral memorized in the numeral register 150 becomes zero uponrepetition of such operation, a signal is emitted from the zero decisioncircuit 154 and fed to the timing control means 152 to stop theoperation of the pulse generator 151. The pulse generator 151 thusstopped no longer generates a step pulse, so that the stepping motorstops rotating. Therefore, if the numeral initially set in the numeralregister 150 is 100 or 1 mm, the stepping motor has been rotated 100steps and the cutting tool mount associating with the clutch which hasbeen in an ON position in this case, has been moved 1.00 mm.

Upon completion of one process as described above, a signal is sent fromthe timing control means 152 to the tape reader 145 to cause it to readthe next information and thereby to carry out a new process. Thereafter,such operation is repeatedv to complete a finished parts. Where it isdesired to obtain a large number of parts of the same type, it is onlynecessary to feed the paper tape to the tape reader in the form ofendless loop repeatedly.

Now, the basic operation of the numerical control unit will be describedby way of practical example. For a process of feeding the fifth cuttingtool 81 a distance of 1.23 mm at-the rate of 300 pulses/second, thepaper tape 144 is perforated as follows:

These symbols are read by the tape reader 145 one after another. Firstof all, T is read by the tape reader and a signal representative of T issent to the decoder 146, indicating that the successive numeral is acutting tool designating code. Then, numeral 5 is read by the tapereader, whereupon the cutting tool selection clutch control means 148 isactuated to energize the clutch for the fifth cutting tool 81.Thus, theclutch pin is projected and the clutch is placed in an ON position. Atthe same time, the motor control means 149 is actuated to energize thecircuit which operates the stepping motor 87 for the cutting tool. Thecharacter S" is read by the tape reader and a signal representative of Sis sent to the decoder 146, indicating that the following numeral is aspeed designating code. Then, numeral 3 which follows is read by thetape reader and a signal representative of 3 is sent to the pulsegenerator 151, whereby the circuit of the pulse generator is set togenerate pulses at the rate of 300 pulses/second. Then, the symbol isread by the tape reader and a signal thereof is fed to the decoder 146.The decoder 146 identifies the +symbol as a rotational directiondesignating code and the motor control means 149 forms a circuit torotate the stepping motor in normal directionsSince the decoder knowsthat the numeral following the symbol is a numeral which controls theposition of the cutting tool, numeral l the numeral l is shifted to thenext higher digit posi tion and numeral 2 is set in the lowest digitposition of the numeral register 150. Similarly, when the next numeral3" is read, the numeral 3'is plated in the lowest digit position of thenumeral register 150 and numerals 1 and 2 are shifted to the next higherdigit position respectively. Thus, numeral 123 is memorized in thenumeral register. A code CR which is to be read next is an operationstart instructing code and the timing control means 152 starts to' tinueto rotate in normal direction. The rotation of the cam shaft 89 and thelinear cam is transmitted to the arm 103 and thence to the fifth cuttingtool 81 to cause the latter to cut the rod material 61. When the numeralmemorized in the numeral register becomes zero, the pulse generatorv 151ceases its operation and the stepping motor 87 stops precisely, evenfrom a high speed because it has a large holding property, and generatesa large braking force. Therefore, the fifth cutting tool 81 ispositively held in a position 1.23 mm from its initial position.

The numericalcontrol system described above belongs to the incrementalopen loop type and hence a step error occurring under some conditions isaccumulated The automatic lathe according to the present invention isprovided with means to eliminate such error. Namely, according to theinvention, the error is eliminated by incorporating a correctioninstructing code in the paper tape in the form of perforations, which isalso read by the tape reader.

First of all, when a correction instruction for the cam shaft 89 is readfrom the tape 144 and identified as a correction instruction by thedecoder 145, the timing control means 152 controls a series ofoperations which will be explained with reference to FIG. 15. In thefollowing explanation, it is considered that the cam is held stationaryand the cam follower moves relative to the cam, for the convenience ofexplanation. The electrical connection is made such that when the camfollower is at a point A, the retraction limit switch is turned on,whereas when the cam follower is at a point B, the origin detector 131is turned on. If a correction instruction is issued when the camfollower is in the position 1 relative to the cam, the pulse generator151 and the motor control means 149 operate so as to cause a reverserotation of the stepping motor 87 at a high speed and the retractionlimit switch is placed in the ON position. This condition lasts until asignal is sent from a check means'l55, shown in FIG. 14, to the timingcontrol means 152. The signal passes through a portion where the origindetector is energized, but in this case the origin switch signal doesnot cause any action nor is the information memorized in the numeralregister 150 changed. I

Upon receiving the retraction limit switch signal, the motor controlmeans 149 switches the circuit of the stepping motor 87 for normalrotation and the frequency of the pulse generated by the pulse generator151 is lowered, so that the motor proceeds at an intermediate speed to apoint where the origin detector is placed in an ON position. When theorigin switch is turned on, the stepping motor 87 is stopped at acertain phase in the exciting phase thereof to effect the correction ata more accurate absolute position, whereby the correction is completed.This will be further explained with reference to the case when thestepping motor is a four-phase exciting motor as shown in FIG. 16.Referring to FIG. 16, symbols L L L, and L designate exciting coils ofthe motor, respectively. The current supply to the exciting coils isregularly switched by two switches SW SW to rotate the motor stepwise ina predetermined direction.

In practice, the switching is effected by means of transistors. If thetiming of the switching operation is determined by pulses P as shown inFIG. 17, the phases of the intermittend current passing through therespective coils are as indicated by the hatching. If the time T is ofthe first phase, the times T T and T are of the second, the third andthe fourth phases. Suppose that the correction completion signal END isto be emitted in the first phase T after the origin switch ORI has beenturned on, the END signal is issued in the time T no matter at whatportion of the period from the point D to the point B of FIG. 17 theorigin switch ORI has been turned on, and the stepping motor is stoppedand the current continues to flow through the coils L and L only toproduce a braking force. This means that the tool mount can be stoppedin a fixed absolute position, even if the position in which the originswitch ORI is turned on is slightly variable within the range from thepoint D to the point E. In the present invention, such a stable andhighly precise position correcting operation is effected at each timewhen the tool mount begin to move, and, therefore, a positional controlfree of error accumulation can be attained, though the system is of theopen loop type.

The cam surface of the linear cam 72 to operate the material feeder 60has a uniform lift and hence the point at which the origin switch isturned on is located near the point A. The positional correction of thematerial feeder 60 is performed in exactly the same manner as thepositional correction of the cutting tool driving shaft. In this case,the collet chuck which holds the rod material 61, is opened to releasethe rod material, retracted and closed again upon completion of thecorrection, all by the function of the solenoid control means 147.Therefore, the rod material is gripped again always with a correctdimension, and by making use of such advantageous feature, it ispossible to obtain a parts longer than the movable range of the materialfeeder 60.

In the present invention, the origin detection signal is used in anotherway, in addition to the way described above. Namely, whether theposition selected under numerical control was correct or not is verifiedby utilizing the origin detection signal in the following manner: Acheck instructing code punched in the paper tape 144 is read by the tapereader 145 and the numeral thus read from the tape 144 is set in thenumeral register 150 as a reference numeral. This reference numeral isthe distance from the present position of the cutting tool to theorigin, plus numeral 4 when the position of the cutting tool is correct.Then, the timing control means perform a series of operations to bedescribed hereunder, in accordance with the operation start instructingcode read by the tape reader 145.

In FIG. 18, the point F is the present position of the cutting tool andthe point G is the origin. The dotted line a is the distance which thecutting tool has already moved under numerical control and the solidline [3 is a reference distance which the cutting tool will move. Firstof all, the motor is set for reverse rotation from the present positionF.

Then, the pulse generator 151 is actuated and the motor is rotated inresponse to the pulse generated by the pulse generator. At the sametime, I is subtracted from the numeral memorized in the numeral register150, by the function of the subtraction circuit 153. When the motorcontinues to rotate and approaches the origin, it passes through thephases shown in FIG. 17, in the order of T T T T and T The checkcompletion signal END is emitted in the phase of T, which is the firstphase after the origin signal ORI has disappeared. The pulse generatorstops its pulse generating operation and the motor is also stopped, sothat the subtraction is interrupted. This position is four steps reversefrom the aforesaid correction point. However, since the referencenumeral is the distance which the cutting tool moves to return to theorigin, plus 4, the numeral memorized in the numeral register becomeszero at this position. Therefore, the correctness of the tool positionis verified by a signal emitted by the zero decision circuit 154. If thenumeral memorized in the numeral register is minus, this means that morepulses than the correct number of pulses, corresponding to that requiredin the case of normal rotation, has been required and the point F hasbeen selected beyond the correct position of the cutting tool.Conversely, if the numeral memorized in the numeral register 150 isplus, this means that the cutting tool has stopped before the point F.In either case, a corrective action is taken as will be described later.

In the present invention, as has been described above, means is providedto preclude an error in the positional control which is possible tooccur unexpectedly in the incremental open loop system, in addition tothe means to correct the origin described previously.

Now, the manner of disposing the completed parts will be describedhereinafter. The operation of removing the completed parts includesthree steps, i.e. the step of separating the parts from the chips, thestep of sorting the parts by the types and the step of removingdefective parts. As shown in FIG. 19, the parts 156 produced by turningthe tip of the rod material 61 is cut from the rod material by means ofa cutting tool 157. In this case, a solenoid 158 is energized from thesolenoid control means 147, to locate a parts delivery chute 159 in aposition below the parts 156. Namely, the chute 159 is pivotablysupported on a pin 160 and constantly biased by a spring 161 but ispositioned below the parts by the action of the solenoid 158, only whenthe parts 156 is dropped. Therefore, the chip will not fall on the chuteduring normal turning operation of the lathe, and the parts are thusseparated from the chip.

The parts 156 cut from the rod material drops and slides on the chute159 and led onto a discrimination chute 162. If three discriminationchutes are in the positions shown in FIG. 19, the parts slides on thediscrimination chutes 162, 163 and drops into a first pocket 164. Thediscrimination chutes 162, 163 and 167 are pivotably mounted on pins168, 169 and 170 and pulled in the same direction by springs 171, 172and 173 respectively. In the state shown in FIG. 19, the respectivechutes are pulled and inclined by solenoids 165, 166 against the biasingforces of the springs. Th us, it will be seen that if the solenoid 166is de-energized, the discrimination chutes 163, 167 will be inclined inthe opposite direction and the parts will be received in a second pocket174 by being guided by the discrimination chutes. Similarly, if thesolenoid is de-energized and the solenoid 166 is energized, the partswill be received in a third pocket 175. Further, if the solenoids 165,166 are both de-energized, the parts will be received in a fourth pocket176. Therefore, by suitably energizing the solenoids 165, 166 accordingto the information punched in the tape 144, the parts can be sorted bythe types. However, if there is an error in the collation or a defectivecondition is detected by the check, the delivery chute 159 will becomeinoperative, even with the information incorporated in the tape 144,afid the defective parts are discarded together with the c ip.

In the turning of a large number of parts, the cutting tools will beworn out gradially or conversely the cutting edges of the cutting toolswill be extended by the material attached thereto. Thus, it becomesnecessary to compensate a change in cutting dimensions caused by suchphenomenone. According to the present invention, an automatic dimensionmeasuring means 177 is provided as shown in FIG. 14, to actually measurethe dimensions of the parts. A dimensional error detected by theautomatic dimension measuring means 177'is' memorized in a compensationregister 178 and the value memorized in the dimension measuring means isadded to or subtracted fromthe numeral memorized in the numeral register150, so as to compensate the dimensional error by changing the cuttingtool control distance by a dimension corresponding to the dimensionalchange of the cutting edge.

The automatic dimension measuring means will be described in furtherdetail hereunder: FIG. shows the detail construction of a parts samplingmechanism for measuring the dimensions of a sample parts. In FIG. 20,the parts sampling mechanism is in a position immediately before theparts 156 is cut from the rod material 61 by the cutting tool. A chuck179 is provided coaxially with the rod material 61, into which one endof the parts 156 is inserted as the rod material 61 is moved forward. Asshown in FIG. 21, the chuck 179 consists of an elastic body having slits179 formed therein and is rotatable with the parts because the parts 156is still rotating when inserted into the chuck 179. Namely, the chuck179 is rotatably mounted on a stationary shaft 180 through a largenumber of balls 180', which stationary shaft is fixedly connected to acover 181 secured to an upper end of an arm 182.'The arm 182 has itslower end pivotally mounted on a shaft 183.

After having been cut from the rod material 61, the parts thus supportedby the chuck 179 is removed from the working position while beingcarried by the arm 182 along an arcuate locus as shown in FIG. 22. Twoupper and lower contactors 184, 185 to measure the diameter of the parts156 are provided at an intermediate position of the arcuate locus andthe parts 156 passes through the interspace of the contactors whileurging the contactors outwardly. The parts thus measured is then knockedout of the chuck 179, and the next parts is measured in the mannerdescribed.

A dimension measuring instrument having the aforesaid contactors 184,185 comprises two T-shaped arms 186, 187 connected together by a pin 188into H- shape, for pivotal movement about the pin. The contactors 184,185 are provided at one confronting ends of the arms 186, 187, while adifferential transformer 189 is provided at the other ends. Thedifferential transformer 189 has a coil 190 disposed therein and acylinderical hollow is formed at the center thereof. A cylindrical core191 of a magnetic material is removably disposed in the cylindricalhollow. This cylindrical core 191 is screw-threaded through a nut .192provided on the arm 186 and is provided with a handle 193 so that theposition thereof may readily be adjusted by rotating the handle. Thearms 186, 187 are biased by a spring 194 to urge the contactors 184,toward each other. However, the space interval between the contactors184, 185 will not become smaller than a predetermined interval because abolt 196 is provided on the arm 186 by a nut 195 for engagement with astopper 197 provided on the arm 187.

When the bolt 196 is in contact with the stopper 197, the core 191within the coil is held in its upper position, whereas when the parts156 is being measured by the measuring instrument as shown in FIG. 21,the core 191 is held in its lower position. Therefore, the verticaldisplacement of the core 191 can be taken out as a voltage change orcurrent phase change. This will be explained with reference to FIG. 23.In FIG. 23, the axis of ordinate represents a change in electric signal(V) corresponding to a displacement of the core 191 and the axis ofabscissa represents time (t). The time referred to here is the period inwhich the parts 156 passes between the contactors 184, 185 withoutstopping. Assuming that the magnitude of the electric signal. duringcalibration of the measuring instrument by means of a parts of correctdimension or a gauge is V0 and a correction value at this time is zero,if the electric signal is changed as indicated by the solid line in FIG.23 during actual measurement of a parts, the dimension of the parts iscorrect and the correction value is zero. However, if the electricsignal is changed as indicated by the dotted line V the dimension of theparts is larger, and conversely if the electric signal is changed asindicated by one-dot chain line V the dimension of the parts is smaller.

A larger dimension means insufficient forward movement of the cuttingtool, so that the correct dimension can be obtained only by adding thecorrection value. Conversely, where the dimension is smaller, thecorrect dimension can be obtained by the subtraction of the correctionvalue.

The automatic dimension measuring means 177 is composed of a circuit asindicated by the block diagram of FIG. 24. Namely, a signal emitted fromthe differential transformer 189 is fed to a head value detectingcircuit 198 which detects and memorizes the peak value of the curveshown in FIG. 23. The peak value thus detected is fed to an averagingcircuit 199 which derives a mean value of the peak value and thepreviously measured values, and the mean value is digitized by ananalog-digital converter circuit 200 and set in the correction register178 shown in FIG. 14. The value thus set in the correction register iszero during calibration, is a plus value when the parts is larger and isa minus value when the parts is smaller. The value is set together witha plus or minus symbol.

Each of the control means shown in FIGS. 14 and 24 consists mainly of adigital circuit comprising electric parts, such as transistors,electrically connected with each other in a known manner, or of suchdigital circuit and an analog circuit combined with a portion thereof,so as to obtain the above-described functions respectively. Although inthe embodiment described and illustrated herein, use is made of a papertape incorporating

1. An automatic lathe comprising an information source means having aworking information fed therein, an electric control device forcontrolling the operation of a driving source means upon reading theworking information, a shaft driven from said driving source means,linear cams each mounted on said shaft and having a cam surface whichdefines an Archimedes curve, and cam followers each being in engagementwith the cam surface of the cooperating linear cam and operativelyconnected to an associated cutting tool mount.
 2. An automatic lathe asdefined in clAim 1, wherein the cam surface of the linear cam consistsof a small diameter portion defining an Archimedes curve of a largercurvature and a large diameter portion defining an Archimedes curve of asmaller curvature.
 3. An automatic lathe as defined in claim 1, whereinthe cam follower is mounted in an arm, connected to the cutting toolmount, through a clutch mechanism so that said cam follower may beslidable relative to or fixed to said arm, and said clutch mechanism isoperated under control of said electric control device.
 4. An automaticlathe as defined in claim 3, wherein a switch is provided on said clutchmechanism to detect an engaged or disengaged position of said clutchmechanism and send a signal to the electric control device.
 5. Anautomatic lathe comprising an information source means having a workinginformation fed therein, an electric control device for controlling theoperation of a driving source means upon reading the workinginformation, a rockable cutting tool mount having a pair of cuttingtools mounted thereon and being rockable about a shaft, a cam followerfixed to said rockable cutting tool mount, a cam follower connected tosaid rockable cutting tool mount through a clutch mechanism, and a pairof linear cams for operating said respective cam followers each having acam surface defining an Archimedes curve and mounted on a common shaftin such a manner that the inclinations of the cam surfaces thereof arein opposite directions to each other, said common shaft being drivenfrom said driving source means.
 6. An automatic lathe comprising anaxially slidable material feeder adapted to grip and rotate a rodmaterial, a cam follower operatively connected to said material feederthrough an arm, a linear cam for operating said cam follower whose camsurface defines an Archimedes curve, a driving source means for drivinga shaft on which said linear cam is fixedly mounted, a plurality ofcutting tool mounts provided in opposed relation to said rod material, aplurality of cam followers each connected to an arm through a clutchmechanism which arm is in turn connected to the associated cutting toolmount, a plurality of linear cams for operating said respective camfollowers each having a cam surface defining an Archimedes curve,another driving source means for driving a common shaft on which saidplurality of linear cams are fixedly mounted, and an electric controldevice for controlling the operations of said two driving source meansand said clutch mechanisms in accordance with the working informationsupplied from said information source means.
 7. An automatic lathecomprising an information source means having a working information fedtherein, an electric control device for controlling the rotation ofstepping motors upon reading the working information, cam shafts drivenfrom said stepping motors respectively, linear cams mounted on saidrespective cam shafts and each having a cam surface defining anArchimedes curve, driven members such as cutting tool mounts and amaterial feeder operatively connected to cam followers in engagementwith said linear cams respectively, a limit switch provided on each ofsaid cam shafts and an origin detector for detecting the origin of eachof said stepping motors; said electric control device including a motorcontrol means for controlling the rotations of said stepping motors, acorrection instructing code for receiving a correction instructions fromthe working information, and a timing control means for sending a signalto said motor control means upon receiving a signal from said correctioninstructing code and signals from said limit switches and said origindetectors and thereby stopping said stepping motors at the originsthereof.
 8. An automatic lathe according to claim 6, wherein saidmaterial feeder comprises a collet chuck for gripping and rotating aworkpiece, the gripping action of said collet chuck being controlled bysaid electric control device.